1. Field of the Invention
Embodiments of the present invention generally relate to deposition processes for a silicon-containing dielectric layer using an improved microwave-assisted CVD chamber.
2. Description of the Related Art
In the manufacture of integrated circuits, chemical vapor deposition (CVD) processes are often used for deposition or etching of various material layers. Examples of common CVD technologies include thermal CVD, low pressure CVD (LPCVD), plasma-enhanced CVD (PECVD), microwave plasma-assisted CVD, atmospheric pressure CVD, and the like. Conventional thermal CVD processes supply reactive compounds to the substrate surface where heat-induced chemical reactions take place to produce a desired layer. Plasma enhanced chemical vapor deposition (PECVD) processes employ a power source (e.g., radio frequency (RF) power or microwave power) coupled to a deposition chamber to increase dissociation of the reactive compounds. Thus, PECVD processes is a prolific and cost effective method for fast growth of materials of good quality at lower substrate temperatures (e.g., about 75° C. to 650° C.) than those required for analogous thermal processes. This is advantageous for processes with stringent thermal budget demands.
As demand for larger flat panel displays and solar panels continues to increase, so must the size of the substrate and hence, the size of the processing chamber. For thin film deposition, it is often desirable to have a high deposition rate to form films on large substrates, and flexibility to control film properties. Higher deposition rate may be achieved by increasing plasma density or lowering the chamber pressure. Microwave plasma-assisted CVD (MPCVD) has been developed to achieve higher plasma densities (e.g. 1011 ions/cm3) and higher deposition rate, as a result of improved power coupling and absorption at 2.45 GHz when compared to typical radio frequency (RF) coupled plasma sources running at 13.56 MHz. One drawback of using RF plasma is that a large portion of the input power is dropped across the plasma sheath (dark space). By using microwave plasma, a narrow plasma sheath is formed and more power can be absorbed by the plasma for creation of radical and ion species. This can increase the plasma density with a narrow energy distribution by reducing collision broadening of the ion energy distribution.
In the past, the main drawback associated with microwave source technology in the vacuum coating industry was the difficulty in maintaining homogeneity during scale up from small wafer processing to very large area substrate processing. Recent advances in microwave reactor design have placed these challenges within reach. Arrays of plasma linear sources have been developed to deposit substantially uniform films of ultra large area (greater than 1 m2) at a high deposition rate to form dense and thick films. However, as the size of the substrate continues to increase, there is a continuing need in the art for improving plasma homogeneity and density to deposit uniform films on a substrate of a large area at a higher deposition rate while making large-scale manufacturing possible at reasonable cost.